There is an ever-increasing need for greater precision with respect to motion generation and position measurement, for purposes of applications commonly referred to as “nanoscale” science and engineering. Examples of relevant applications include manufacture of nanoscale structures, atomic-level handling and manipulation of materials, assembly and packaging of microparts, vibration isolation for delicate instrumentation, seismic motion detection, human-computer interfaces for dexterous robotics, and motion/force feedback for applications such as virtual reality and telepresence situations.
In regard to telepresence situations, teleoperations in robotics and manufacturing is an emerging technology that can extend the range of human activities. For example, humans can use robots to perform dexterous manipulation, without exposing themselves to harsh and remote environments, such as space or nuclear reactors. As another example, telepresence surgery by a surgeon is gaining popularity, in part because it permits a specialist located in one city to perform a sophisticated surgical operation on a patient located in a different city. In telepresence surgery, high fidelity force and tactile reflection is need to enhance sensitivity.
As another example of an application needing high-resolution motion generation and position measurement, research is being conducted regarding what is known as nano-pinning phenomenon in type II high temperature superconductive materials, and its possible application to next-generation mass data storage devices which have storage densities in excess of 1010 bits per square centimeter. The pinning process dopes atoms into a type II high-temperature thin film crystalline superconductor structure, with 5 nanometer separation. Recording and erasing data on this lattice structure can be achieved by precisely positioning a magnetic force microscope (MFM) head over the pinning sites. However, a significant technical hurdle to possible implementation of such devices is the need for equipment that can achieve positioning with nanometer-level resolution and repeatability, because pre-existing technologies are not well suited to this task.
Still another potential application relates to the fabrication of integrated circuits. During the next few years, the critical size for integrated circuit devices is expected to be approximately 100 nanometers. Consequently the overlay accuracy needed for photolithography equipment (such as wafer steppers and scanners) during fabrication of these devices should be about 20 nanometers, or better. Pre-existing technologies present difficulties in achieving this level of accuracy.
Various different approaches have previously been developed, in an attempt to provide suitable motion generation and position detection for small-scale applications. However, many of these approaches involve complex mechanical elements and linkages, which are relatively expensive, and in which tolerances can accumulate in a manner that reduces resolution. Also, many of the existing approaches utilize precision bearing surfaces, but even precision bearing surfaces can involve non-linear and stochastic problems such as friction, stiction, backlash and the like. Further, precision bearing surfaces contribute to increased manufacturing expense.
In one pre-existing approach, which avoids some of these problems, a movable part is magnetically levitated, and can be controlled in multiple degrees of freedom. However, while pre-existing magnetic levitation systems have been generally adequate for some applications, they have not been satisfactory in all respects. For example, the movable part typically has one or more electrically energized coils, which cause heating of the moving part due to dissipation of heat within the coils. Further, an umbilical cable is needed for the moving part, in order to carry control signals to the coils, but it is possible for the umbilical cable to transmit vibrations to the moving part in a magnitude which is significant in comparison to the nano-scale positioning and resolution needed for many applications. Further, the moving part typically has a relatively heavy weight, due in part to the coils thereon. The weight affects the natural frequencies of the system, and decreases the response time.